The original creator of this library (or demo, I'm not quite sure), Dan, left BYOND almost a decade ago. It looks like DEBUG_NOTICE() is only supposed to be compiled if the world is in DEBUG mode, but that isn't the case anymore. BYOND may have modified how preprocessors worked (considering this is twelve years old, that's most likely it.)

As for the duplicate variable issue, just rename one of them to something else.

It also looks like all of the icons packaged in this are corrupted. Hrm. I'll have to see about getting those fixed.